ABOUT THIS PRIMARY: Incumbent District 6 St. Louis County Commissioner Keith Nelson of Eveleth is being challenged this year by John Moren of Canyon and Matt Matasich of Virginia. Two will advance from the Aug. 9 primary to Election Day on Nov. 8. All three were invited by the News Tribune Opinion page to write a column about their candidacies and qualifications. Commissioner Nelson declined. District 6 stretches from about Mountain Iron in the north to about Twig in the south.